# Need Help about fortran (g77)

1. Mar 12, 2009

### paulga

I came across a problem on the project:
my project is comprised of tens of fortran files. There is a param.h header file collecting all the parameters that are used by the program and subroutines. but after I add this line:
parameter(pi = dacos(-1.0d0))
into the param.h
the command "make " always reports errors like:

param.h: In subroutine stressinit':
param.h:135:
parameter(pi = dacos(-1.0d0))
^
Invalid declaration of or reference to symbol dacos' at (^) [initially seen at (^)]

How to employ the function "dacos" in a header file?
Thanks a lot.